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Speaker 1: Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff,

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Speaker 1: I'm Lauren vogel Bomb, and we've all had moments of

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Speaker 1: uncertainty and, let's face it, paranoia about the state of

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Speaker 1: the food sitting in our refrigerators. You might be able

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Speaker 1: to eyeball some of the suspicious items, check for expiration

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Speaker 1: dates on others, and with some milk maybe you'll probably

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Speaker 1: take a quick whiff and hope for the best. But

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Speaker 1: if you've ever looked a shelf life chart to figure

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Speaker 1: out how long your milk might last, you might have

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Speaker 1: noticed that skim milk is said to last a day

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Speaker 1: or two longer than whole milk. But is that really

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Speaker 1: true and if so, why? Before we really get started,

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Speaker 1: I should state that there is by no means universal

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Speaker 1: agreement on this issue. Some dairy scientists say skim milk

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Speaker 1: lasts longer because certain fat loving microbes can't develop as

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Speaker 1: quickly in non fat milk. Others say that whole milk

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Speaker 1: lasts longer because free fatty acids might actually be natural preservatives. Still,

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Speaker 1: others say that maybe there isn't a difference in spoilage

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Speaker 1: at all, it's just that we notice flavor changes more

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Speaker 1: in one or the other. There's only been one major

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Speaker 1: controlled study on the spoilage rates of whole and skim milk,

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Speaker 1: and it was somewhat inconclusive. Skim milk was found to

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Speaker 1: spoil slightly faster, but the researchers weren't exactly sure why.

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Speaker 1: Bacteria that are psychotrophic, that is, cold resistant, are what

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Speaker 1: caused spoilage in the fridge, and in the study, they

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Speaker 1: multiplied at the same rate in both types of milk.

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Speaker 1: When the milk spoiled, both whole and skim contained similar

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Speaker 1: strains of bacteria. There was a pronounced difference and how

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Speaker 1: whole and skim milk reacted when they were injected with

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Speaker 1: the same spoilage microorganisms, but they affected the milks taste

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Speaker 1: and smell more than they did the actual spoilage rate.

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Speaker 1: Whole milk, for the record, tended to turn sour and

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Speaker 1: skim milk was on the bitter side. So for the

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Speaker 1: purposes of your average milk consumer, there's really no hard

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Speaker 1: and fast rule about which kind will spoil faster. If

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Speaker 1: whole milk does last longer than skim, the difference is

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Speaker 1: so slight that any given gallon of skim milk could

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Speaker 1: outlast any given gallon of whole milk. The spoilage rate

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Speaker 1: depends on so many variables manufacturer production methods, milk formulation,

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Speaker 1: plant sanitation, storage temperatures, pH level, moisture content, just to

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Speaker 1: name a few. A small change in just one of

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Speaker 1: them could give any particular container of milk a slightly

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Speaker 1: longer shelf life than another. A couple other factors make

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Speaker 1: things even more ambiguous. For one, it's pretty much impossible

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Speaker 1: to pinpoint the exact moment of spoilage. Depending on your

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Speaker 1: sense of smell and taste and your tolerance for changes

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Speaker 1: in milk flavor, you might turn up your nose at

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Speaker 1: a gallon of milk that someone else might readily swig.

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Speaker 1: And there's no federal regulation of milk expiration dates in

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Speaker 1: the United States. Only twenty states legally standardized the date

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Speaker 1: that's printed on the bottle, and those standards vary widely.

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Speaker 1: One state might mandate a cell by date of a

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Speaker 1: certain number of days after pasteurization, whereas milk jugs and

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Speaker 1: another state would be printed with a use by date.

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Speaker 1: The upshot don't base your milk purchases on which type

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Speaker 1: might last longer. If you're concerned about shelf life. You'd

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Speaker 1: be better off following a few simple steps to slow

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Speaker 1: down milk spoilage, whether you're a whole or skim drinker. First,

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Speaker 1: make sure your refrigerator is the correct temperature. It should

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Speaker 1: be set at forty degrees fahrenheit that's four point four

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Speaker 1: degrees celsius. Store your milk on an interior shelf instead

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Speaker 1: of on the door, which fluctuates more in temperature. And

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Speaker 1: make sure you put your milk back in the fridge

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Speaker 1: as soon as possible after using it. Leaving it out

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Speaker 1: on the counter for even a few minutes exposes it

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Speaker 1: to light and heat, giving bacteria a chance to spring

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Speaker 1: into action. Today's episode was written by Alison Cooper and

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Speaker 1: produced by Tyler Clang. Bonus fact for the episode, the

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Speaker 1: origin of milks expiration date labels and of expiration date

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Speaker 1: labels in general in the United States rests with a

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Speaker 1: campaign started by al Capone. To learn more about that,

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Speaker 1: check out an episode of my other podcast, Saber. The

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Speaker 1: episode is called expiration Dates Best if listened by and

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Speaker 1: of course, for more on this and lots of other

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Speaker 1: fresh topics, visit our home planet pastuff works dot com.